remoting/codec/video_encoder_vpx.cc - chromium/src.git - Git at Google

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 #include "remoting/codec/video_encoder_vpx.h"

 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/sys_info.h"
 #include "remoting/base/util.h"
 #include "remoting/proto/video.pb.h"
 #include "third_party/libyuv/include/libyuv/convert_from_argb.h"
 #include "third_party/webrtc/modules/desktop_capture/desktop_frame.h"
 #include "third_party/webrtc/modules/desktop_capture/desktop_geometry.h"
 #include "third_party/webrtc/modules/desktop_capture/desktop_region.h"

 extern "C" {
 #define VPX_CODEC_DISABLE_COMPAT 1
 #include "third_party/libvpx/source/libvpx/vpx/vpx_encoder.h"
 #include "third_party/libvpx/source/libvpx/vpx/vp8cx.h"
 }

 namespace remoting {

 namespace {

 // Name of command-line flag to enable VP9 to use I444 by default.
 const char kEnableI444SwitchName[] = "enable-i444";

 // Number of bytes in an RGBx pixel.
 const int kBytesPerRgbPixel = 4;

 // Defines the dimension of a macro block. This is used to compute the active
 // map for the encoder.
 const int kMacroBlockSize = 16;

 // Magic encoder profile numbers for I420 and I444 input formats.
 const int kVp9I420ProfileNumber = 0;
 const int kVp9I444ProfileNumber = 1;

 void SetCommonCodecParameters(const webrtc::DesktopSize& size,
                               vpx_codec_enc_cfg_t* config) {
   // Use millisecond granularity time base.
   config->g_timebase.num = 1;
   config->g_timebase.den = 1000;

   // Adjust default target bit-rate to account for actual desktop size.
   config->rc_target_bitrate = size.width() * size.height() *
       config->rc_target_bitrate / config->g_w / config->g_h;

   config->g_w = size.width();
   config->g_h = size.height();
   config->g_pass = VPX_RC_ONE_PASS;

   // Start emitting packets immediately.
   config->g_lag_in_frames = 0;

   // Using 2 threads gives a great boost in performance for most systems with
   // adequate processing power. NB: Going to multiple threads on low end
   // windows systems can really hurt performance.
   // http://crbug.com/99179
   config->g_threads = (base::SysInfo::NumberOfProcessors() > 2) ? 2 : 1;
 }

 ScopedVpxCodec CreateVP8Codec(const webrtc::DesktopSize& size) {
   ScopedVpxCodec codec(new vpx_codec_ctx_t);

   // Configure the encoder.
   vpx_codec_enc_cfg_t config;
   const vpx_codec_iface_t* algo = vpx_codec_vp8_cx();
   CHECK(algo);
   vpx_codec_err_t ret = vpx_codec_enc_config_default(algo, &config, 0);
   if (ret != VPX_CODEC_OK)
     return ScopedVpxCodec();

   SetCommonCodecParameters(size, &config);

   // Value of 2 means using the real time profile. This is basically a
   // redundant option since we explicitly select real time mode when doing
   // encoding.
   config.g_profile = 2;

   // Clamping the quantizer constrains the worst-case quality and CPU usage.
   config.rc_min_quantizer = 20;
   config.rc_max_quantizer = 30;

   if (vpx_codec_enc_init(codec.get(), algo, &config, 0))
     return ScopedVpxCodec();

   // Value of 16 will have the smallest CPU load. This turns off subpixel
   // motion search.
   if (vpx_codec_control(codec.get(), VP8E_SET_CPUUSED, 16))
     return ScopedVpxCodec();

   // Use the lowest level of noise sensitivity so as to spend less time
   // on motion estimation and inter-prediction mode.
   if (vpx_codec_control(codec.get(), VP8E_SET_NOISE_SENSITIVITY, 0))
     return ScopedVpxCodec();

   return codec.Pass();
 }

 ScopedVpxCodec CreateVP9Codec(const webrtc::DesktopSize& size,
                               bool lossless_color,
                               bool lossless_encode) {
   ScopedVpxCodec codec(new vpx_codec_ctx_t);

   // Configure the encoder.
   vpx_codec_enc_cfg_t config;
   const vpx_codec_iface_t* algo = vpx_codec_vp9_cx();
   CHECK(algo);
   vpx_codec_err_t ret = vpx_codec_enc_config_default(algo, &config, 0);
   if (ret != VPX_CODEC_OK)
     return ScopedVpxCodec();

   SetCommonCodecParameters(size, &config);

   // Configure VP9 for I420 or I444 source frames.
   config.g_profile =
       lossless_color ? kVp9I444ProfileNumber : kVp9I420ProfileNumber;

   if (lossless_encode) {
     // Disable quantization entirely, putting the encoder in "lossless" mode.
     config.rc_min_quantizer = 0;
     config.rc_max_quantizer = 0;
   } else {
     // Lossy encode using the same settings as for VP8.
     config.rc_min_quantizer = 20;
     config.rc_max_quantizer = 30;
   }

   if (vpx_codec_enc_init(codec.get(), algo, &config, 0))
     return ScopedVpxCodec();

   // Request the lowest-CPU usage that VP9 supports, which depends on whether
   // we are encoding lossy or lossless.
   // Note that this is configured via the same parameter as for VP8.
   int cpu_used = lossless_encode ? 5 : 7;
   if (vpx_codec_control(codec.get(), VP8E_SET_CPUUSED, cpu_used))
     return ScopedVpxCodec();

   // Use the lowest level of noise sensitivity so as to spend less time
   // on motion estimation and inter-prediction mode.
   // Note that this is configured via the same parameter as for VP8.
   if (vpx_codec_control(codec.get(), VP8E_SET_NOISE_SENSITIVITY, 0))
     return ScopedVpxCodec();

   return codec.Pass();
 }

 void CreateImage(bool use_i444,
                  const webrtc::DesktopSize& size,
                  scoped_ptr<vpx_image_t>* out_image,
                  scoped_ptr<uint8[]>* out_image_buffer) {
   DCHECK(!size.is_empty());

   scoped_ptr<vpx_image_t> image(new vpx_image_t());
   memset(image.get(), 0, sizeof(vpx_image_t));

   // libvpx seems to require both to be assigned.
   image->d_w = size.width();
   image->w = size.width();
   image->d_h = size.height();
   image->h = size.height();

   // libvpx should derive chroma shifts from|fmt| but currently has a bug:
   // https://code.google.com/p/webm/issues/detail?id=627
   if (use_i444) {
     image->fmt = VPX_IMG_FMT_I444;
     image->x_chroma_shift = 0;
     image->y_chroma_shift = 0;
   } else { // I420
     image->fmt = VPX_IMG_FMT_YV12;
     image->x_chroma_shift = 1;
     image->y_chroma_shift = 1;
   }

   // libyuv's fast-path requires 16-byte aligned pointers and strides, so pad
   // the Y, U and V planes' strides to multiples of 16 bytes.
   const int y_stride = ((image->w - 1) & ~15) + 16;
   const int uv_unaligned_stride = y_stride >> image->x_chroma_shift;
   const int uv_stride = ((uv_unaligned_stride - 1) & ~15) + 16;

   // libvpx accesses the source image in macro blocks, and will over-read
   // if the image is not padded out to the next macroblock: crbug.com/119633.
   // Pad the Y, U and V planes' height out to compensate.
   // Assuming macroblocks are 16x16, aligning the planes' strides above also
   // macroblock aligned them.
   DCHECK_EQ(16, kMacroBlockSize);
   const int y_rows = ((image->h - 1) & ~(kMacroBlockSize-1)) + kMacroBlockSize;
   const int uv_rows = y_rows >> image->y_chroma_shift;

   // Allocate a YUV buffer large enough for the aligned data & padding.
   const int buffer_size = y_stride * y_rows + 2*uv_stride * uv_rows;
   scoped_ptr<uint8[]> image_buffer(new uint8[buffer_size]);

   // Reset image value to 128 so we just need to fill in the y plane.
   memset(image_buffer.get(), 128, buffer_size);

   // Fill in the information for |image_|.
   unsigned char* uchar_buffer =
       reinterpret_cast<unsigned char*>(image_buffer.get());
   image->planes[0] = uchar_buffer;
   image->planes[1] = image->planes[0] + y_stride * y_rows;
   image->planes[2] = image->planes[1] + uv_stride * uv_rows;
   image->stride[0] = y_stride;
   image->stride[1] = uv_stride;
   image->stride[2] = uv_stride;

   *out_image = image.Pass();
   *out_image_buffer = image_buffer.Pass();
 }

 } // namespace

 // static
 scoped_ptr<VideoEncoderVpx> VideoEncoderVpx::CreateForVP8() {
   return scoped_ptr<VideoEncoderVpx>(new VideoEncoderVpx(false));
 }

 // static
 scoped_ptr<VideoEncoderVpx> VideoEncoderVpx::CreateForVP9() {
   return scoped_ptr<VideoEncoderVpx>(new VideoEncoderVpx(true));
 }

 VideoEncoderVpx::~VideoEncoderVpx() {}

 void VideoEncoderVpx::SetLosslessEncode(bool want_lossless) {
   if (use_vp9_ && (want_lossless != lossless_encode_)) {
     lossless_encode_ = want_lossless;
     codec_.reset(); // Force encoder re-initialization.
   }
 }

 void VideoEncoderVpx::SetLosslessColor(bool want_lossless) {
   if (use_vp9_ && (want_lossless != lossless_color_)) {
     lossless_color_ = want_lossless;
     codec_.reset(); // Force encoder re-initialization.
   }
 }

 scoped_ptr<VideoPacket> VideoEncoderVpx::Encode(
     const webrtc::DesktopFrame& frame) {
   DCHECK_LE(32, frame.size().width());
   DCHECK_LE(32, frame.size().height());

   base::TimeTicks encode_start_time = base::TimeTicks::Now();

   if (!codec_ ||
       !frame.size().equals(webrtc::DesktopSize(image_->w, image_->h))) {
     bool ret = Initialize(frame.size());
     // TODO(hclam): Handle error better.
     CHECK(ret) << "Initialization of encoder failed";

     // Set now as the base for timestamp calculation.
     timestamp_base_ = encode_start_time;
   }

   // Convert the updated capture data ready for encode.
   webrtc::DesktopRegion updated_region;
   PrepareImage(frame, &updated_region);

   // Update active map based on updated region.
   PrepareActiveMap(updated_region);

   // Apply active map to the encoder.
   vpx_active_map_t act_map;
   act_map.rows = active_map_height_;
   act_map.cols = active_map_width_;
   act_map.active_map = active_map_.get();
   if (vpx_codec_control(codec_.get(), VP8E_SET_ACTIVEMAP, &act_map)) {
     LOG(ERROR) << "Unable to apply active map";
   }

   // Do the actual encoding.
   int timestamp = (encode_start_time - timestamp_base_).InMilliseconds();
   vpx_codec_err_t ret = vpx_codec_encode(
       codec_.get(), image_.get(), timestamp, 1, 0, VPX_DL_REALTIME);
   DCHECK_EQ(ret, VPX_CODEC_OK)
       << "Encoding error: " << vpx_codec_err_to_string(ret) << "\n"
       << "Details: " << vpx_codec_error(codec_.get()) << "\n"
       << vpx_codec_error_detail(codec_.get());

   // Read the encoded data.
   vpx_codec_iter_t iter = NULL;
   bool got_data = false;

   // TODO(hclam): Make sure we get exactly one frame from the packet.
   // TODO(hclam): We should provide the output buffer to avoid one copy.
   scoped_ptr<VideoPacket> packet(new VideoPacket());

   while (!got_data) {
     const vpx_codec_cx_pkt_t* vpx_packet =
         vpx_codec_get_cx_data(codec_.get(), &iter);
     if (!vpx_packet)
       continue;

     switch (vpx_packet->kind) {
       case VPX_CODEC_CX_FRAME_PKT:
         got_data = true;
         packet->set_data(vpx_packet->data.frame.buf, vpx_packet->data.frame.sz);
         break;
       default:
         break;
     }
   }

   // Construct the VideoPacket message.
   packet->mutable_format()->set_encoding(VideoPacketFormat::ENCODING_VP8);
   packet->mutable_format()->set_screen_width(frame.size().width());
   packet->mutable_format()->set_screen_height(frame.size().height());
   packet->set_capture_time_ms(frame.capture_time_ms());
   packet->set_encode_time_ms(
       (base::TimeTicks::Now() - encode_start_time).InMillisecondsRoundedUp());
   if (!frame.dpi().is_zero()) {
     packet->mutable_format()->set_x_dpi(frame.dpi().x());
     packet->mutable_format()->set_y_dpi(frame.dpi().y());
   }
   for (webrtc::DesktopRegion::Iterator r(updated_region); !r.IsAtEnd();
        r.Advance()) {
     Rect* rect = packet->add_dirty_rects();
     rect->set_x(r.rect().left());
     rect->set_y(r.rect().top());
     rect->set_width(r.rect().width());
     rect->set_height(r.rect().height());
   }

   return packet.Pass();
 }

 VideoEncoderVpx::VideoEncoderVpx(bool use_vp9)
     : use_vp9_(use_vp9),
       lossless_encode_(false),
       lossless_color_(false),
       active_map_width_(0),
       active_map_height_(0) {
   if (use_vp9_) {
     // Use I444 colour space, by default, if specified on the command-line.
     if (CommandLine::ForCurrentProcess()->HasSwitch(kEnableI444SwitchName)) {
       SetLosslessColor(true);
     }
   }
 }

 bool VideoEncoderVpx::Initialize(const webrtc::DesktopSize& size) {
   DCHECK(use_vp9_ || !lossless_color_);
   DCHECK(use_vp9_ || !lossless_encode_);

   codec_.reset();

   // (Re)Create the VPX image structure and pixel buffer.
   CreateImage(lossless_color_, size, &image_, &image_buffer_);

   // Initialize active map.
   active_map_width_ = (image_->w + kMacroBlockSize - 1) / kMacroBlockSize;
   active_map_height_ = (image_->h + kMacroBlockSize - 1) / kMacroBlockSize;
   active_map_.reset(new uint8[active_map_width_ * active_map_height_]);

   // (Re)Initialize the codec.
   if (use_vp9_) {
     codec_ = CreateVP9Codec(size, lossless_color_, lossless_encode_);
   } else {
     codec_ = CreateVP8Codec(size);
   }

   return codec_;
 }

 void VideoEncoderVpx::PrepareImage(const webrtc::DesktopFrame& frame,
                                    webrtc::DesktopRegion* updated_region) {
   if (frame.updated_region().is_empty()) {
     updated_region->Clear();
     return;
   }

   // Align the region to macroblocks, to avoid encoding artefacts.
   // This also ensures that all rectangles have even-aligned top-left, which
   // is required for ConvertRGBToYUVWithRect() to work.
   std::vector<webrtc::DesktopRect> aligned_rects;
   for (webrtc::DesktopRegion::Iterator r(frame.updated_region());
        !r.IsAtEnd(); r.Advance()) {
     const webrtc::DesktopRect& rect = r.rect();
     aligned_rects.push_back(AlignRect(webrtc::DesktopRect::MakeLTRB(
         rect.left(), rect.top(), rect.right(), rect.bottom())));
   }
   DCHECK(!aligned_rects.empty());
   updated_region->Clear();
   updated_region->AddRects(&aligned_rects[0], aligned_rects.size());

   // Clip back to the screen dimensions, in case they're not macroblock aligned.
   // The conversion routines don't require even width & height, so this is safe
   // even if the source dimensions are not even.
   updated_region->IntersectWith(
       webrtc::DesktopRect::MakeWH(image_->w, image_->h));

   // Convert the updated region to YUV ready for encoding.
   const uint8* rgb_data = frame.data();
   const int rgb_stride = frame.stride();
   const int y_stride = image_->stride[0];
   DCHECK_EQ(image_->stride[1], image_->stride[2]);
   const int uv_stride = image_->stride[1];
   uint8* y_data = image_->planes[0];
   uint8* u_data = image_->planes[1];
   uint8* v_data = image_->planes[2];

   switch (image_->fmt) {
     case VPX_IMG_FMT_I444:
       for (webrtc::DesktopRegion::Iterator r(*updated_region); !r.IsAtEnd();
            r.Advance()) {
         const webrtc::DesktopRect& rect = r.rect();
         int rgb_offset = rgb_stride * rect.top() +
                          rect.left() * kBytesPerRgbPixel;
         int yuv_offset = uv_stride * rect.top() + rect.left();
         libyuv::ARGBToI444(rgb_data + rgb_offset, rgb_stride,
                            y_data + yuv_offset, y_stride,
                            u_data + yuv_offset, uv_stride,
                            v_data + yuv_offset, uv_stride,
                            rect.width(), rect.height());
       }
       break;
     case VPX_IMG_FMT_YV12:
       for (webrtc::DesktopRegion::Iterator r(*updated_region); !r.IsAtEnd();
            r.Advance()) {
         const webrtc::DesktopRect& rect = r.rect();
         int rgb_offset = rgb_stride * rect.top() +
                          rect.left() * kBytesPerRgbPixel;
         int y_offset = y_stride * rect.top() + rect.left();
         int uv_offset = uv_stride * rect.top() / 2 + rect.left() / 2;
         libyuv::ARGBToI420(rgb_data + rgb_offset, rgb_stride,
                            y_data + y_offset, y_stride,
                            u_data + uv_offset, uv_stride,
                            v_data + uv_offset, uv_stride,
                            rect.width(), rect.height());
       }
       break;
     default:
       NOTREACHED();
       break;
   }
 }

 void VideoEncoderVpx::PrepareActiveMap(
     const webrtc::DesktopRegion& updated_region) {
   // Clear active map first.
   memset(active_map_.get(), 0, active_map_width_ * active_map_height_);

   // Mark updated areas active.
   for (webrtc::DesktopRegion::Iterator r(updated_region); !r.IsAtEnd();
        r.Advance()) {
     const webrtc::DesktopRect& rect = r.rect();
     int left = rect.left() / kMacroBlockSize;
     int right = (rect.right() - 1) / kMacroBlockSize;
     int top = rect.top() / kMacroBlockSize;
     int bottom = (rect.bottom() - 1) / kMacroBlockSize;
     DCHECK_LT(right, active_map_width_);
     DCHECK_LT(bottom, active_map_height_);

     uint8* map = active_map_.get() + top * active_map_width_;
     for (int y = top; y <= bottom; ++y) {
       for (int x = left; x <= right; ++x)
         map[x] = 1;
       map += active_map_width_;
     }
   }
 }

 }  // namespace remoting
	// Copyright 2013 The Chromium Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	#include "remoting/codec/video_encoder_vpx.h"

	#include "base/bind.h"
	#include "base/command_line.h"
	#include "base/logging.h"
	#include "base/sys_info.h"
	#include "remoting/base/util.h"
	#include "remoting/proto/video.pb.h"
	#include "third_party/libyuv/include/libyuv/convert_from_argb.h"
	#include "third_party/webrtc/modules/desktop_capture/desktop_frame.h"
	#include "third_party/webrtc/modules/desktop_capture/desktop_geometry.h"
	#include "third_party/webrtc/modules/desktop_capture/desktop_region.h"

	extern "C" {
	#define VPX_CODEC_DISABLE_COMPAT 1
	#include "third_party/libvpx/source/libvpx/vpx/vpx_encoder.h"
	#include "third_party/libvpx/source/libvpx/vpx/vp8cx.h"
	}

	namespace remoting {

	namespace {

	// Name of command-line flag to enable VP9 to use I444 by default.
	const char kEnableI444SwitchName[] = "enable-i444";

	// Number of bytes in an RGBx pixel.
	const int kBytesPerRgbPixel = 4;

	// Defines the dimension of a macro block. This is used to compute the active
	// map for the encoder.
	const int kMacroBlockSize = 16;

	// Magic encoder profile numbers for I420 and I444 input formats.
	const int kVp9I420ProfileNumber = 0;
	const int kVp9I444ProfileNumber = 1;

	void SetCommonCodecParameters(const webrtc::DesktopSize& size,
	vpx_codec_enc_cfg_t* config) {
	// Use millisecond granularity time base.
	config->g_timebase.num = 1;
	config->g_timebase.den = 1000;

	// Adjust default target bit-rate to account for actual desktop size.
	config->rc_target_bitrate = size.width() * size.height() *
	config->rc_target_bitrate / config->g_w / config->g_h;

	config->g_w = size.width();
	config->g_h = size.height();
	config->g_pass = VPX_RC_ONE_PASS;

	// Start emitting packets immediately.
	config->g_lag_in_frames = 0;

	// Using 2 threads gives a great boost in performance for most systems with
	// adequate processing power. NB: Going to multiple threads on low end
	// windows systems can really hurt performance.
	// http://crbug.com/99179
	config->g_threads = (base::SysInfo::NumberOfProcessors() > 2) ? 2 : 1;
	}

	ScopedVpxCodec CreateVP8Codec(const webrtc::DesktopSize& size) {
	ScopedVpxCodec codec(new vpx_codec_ctx_t);

	// Configure the encoder.
	vpx_codec_enc_cfg_t config;
	const vpx_codec_iface_t* algo = vpx_codec_vp8_cx();
	CHECK(algo);
	vpx_codec_err_t ret = vpx_codec_enc_config_default(algo, &config, 0);
	if (ret != VPX_CODEC_OK)
	return ScopedVpxCodec();

	SetCommonCodecParameters(size, &config);

	// Value of 2 means using the real time profile. This is basically a
	// redundant option since we explicitly select real time mode when doing
	// encoding.
	config.g_profile = 2;

	// Clamping the quantizer constrains the worst-case quality and CPU usage.
	config.rc_min_quantizer = 20;
	config.rc_max_quantizer = 30;

	if (vpx_codec_enc_init(codec.get(), algo, &config, 0))
	return ScopedVpxCodec();

	// Value of 16 will have the smallest CPU load. This turns off subpixel
	// motion search.
	if (vpx_codec_control(codec.get(), VP8E_SET_CPUUSED, 16))
	return ScopedVpxCodec();

	// Use the lowest level of noise sensitivity so as to spend less time
	// on motion estimation and inter-prediction mode.
	if (vpx_codec_control(codec.get(), VP8E_SET_NOISE_SENSITIVITY, 0))
	return ScopedVpxCodec();

	return codec.Pass();
	}

	ScopedVpxCodec CreateVP9Codec(const webrtc::DesktopSize& size,
	bool lossless_color,
	bool lossless_encode) {
	ScopedVpxCodec codec(new vpx_codec_ctx_t);

	// Configure the encoder.
	vpx_codec_enc_cfg_t config;
	const vpx_codec_iface_t* algo = vpx_codec_vp9_cx();
	CHECK(algo);
	vpx_codec_err_t ret = vpx_codec_enc_config_default(algo, &config, 0);
	if (ret != VPX_CODEC_OK)
	return ScopedVpxCodec();

	SetCommonCodecParameters(size, &config);

	// Configure VP9 for I420 or I444 source frames.
	config.g_profile =
	lossless_color ? kVp9I444ProfileNumber : kVp9I420ProfileNumber;

	if (lossless_encode) {
	// Disable quantization entirely, putting the encoder in "lossless" mode.
	config.rc_min_quantizer = 0;
	config.rc_max_quantizer = 0;
	} else {
	// Lossy encode using the same settings as for VP8.
	config.rc_min_quantizer = 20;
	config.rc_max_quantizer = 30;
	}

	if (vpx_codec_enc_init(codec.get(), algo, &config, 0))
	return ScopedVpxCodec();

	// Request the lowest-CPU usage that VP9 supports, which depends on whether
	// we are encoding lossy or lossless.
	// Note that this is configured via the same parameter as for VP8.
	int cpu_used = lossless_encode ? 5 : 7;
	if (vpx_codec_control(codec.get(), VP8E_SET_CPUUSED, cpu_used))
	return ScopedVpxCodec();

	// Use the lowest level of noise sensitivity so as to spend less time
	// on motion estimation and inter-prediction mode.
	// Note that this is configured via the same parameter as for VP8.
	if (vpx_codec_control(codec.get(), VP8E_SET_NOISE_SENSITIVITY, 0))
	return ScopedVpxCodec();

	return codec.Pass();
	}

	void CreateImage(bool use_i444,
	const webrtc::DesktopSize& size,
	scoped_ptr<vpx_image_t>* out_image,
	scoped_ptr<uint8[]>* out_image_buffer) {
	DCHECK(!size.is_empty());

	scoped_ptr<vpx_image_t> image(new vpx_image_t());
	memset(image.get(), 0, sizeof(vpx_image_t));

	// libvpx seems to require both to be assigned.
	image->d_w = size.width();
	image->w = size.width();
	image->d_h = size.height();
	image->h = size.height();

	// libvpx should derive chroma shifts from\|fmt\| but currently has a bug:
	// https://code.google.com/p/webm/issues/detail?id=627
	if (use_i444) {
	image->fmt = VPX_IMG_FMT_I444;
	image->x_chroma_shift = 0;
	image->y_chroma_shift = 0;
	} else { // I420
	image->fmt = VPX_IMG_FMT_YV12;
	image->x_chroma_shift = 1;
	image->y_chroma_shift = 1;
	}

	// libyuv's fast-path requires 16-byte aligned pointers and strides, so pad
	// the Y, U and V planes' strides to multiples of 16 bytes.
	const int y_stride = ((image->w - 1) & ~15) + 16;
	const int uv_unaligned_stride = y_stride >> image->x_chroma_shift;
	const int uv_stride = ((uv_unaligned_stride - 1) & ~15) + 16;

	// libvpx accesses the source image in macro blocks, and will over-read
	// if the image is not padded out to the next macroblock: crbug.com/119633.
	// Pad the Y, U and V planes' height out to compensate.
	// Assuming macroblocks are 16x16, aligning the planes' strides above also
	// macroblock aligned them.
	DCHECK_EQ(16, kMacroBlockSize);
	const int y_rows = ((image->h - 1) & ~(kMacroBlockSize-1)) + kMacroBlockSize;
	const int uv_rows = y_rows >> image->y_chroma_shift;

	// Allocate a YUV buffer large enough for the aligned data & padding.
	const int buffer_size = y_stride * y_rows + 2uv_stride uv_rows;
	scoped_ptr<uint8[]> image_buffer(new uint8[buffer_size]);

	// Reset image value to 128 so we just need to fill in the y plane.
	memset(image_buffer.get(), 128, buffer_size);

	// Fill in the information for \|image_\|.
	unsigned char* uchar_buffer =
	reinterpret_cast<unsigned char*>(image_buffer.get());
	image->planes[0] = uchar_buffer;
	image->planes[1] = image->planes[0] + y_stride * y_rows;
	image->planes[2] = image->planes[1] + uv_stride * uv_rows;
	image->stride[0] = y_stride;
	image->stride[1] = uv_stride;
	image->stride[2] = uv_stride;

	*out_image = image.Pass();
	*out_image_buffer = image_buffer.Pass();
	}

	} // namespace

	// static
	scoped_ptr<VideoEncoderVpx> VideoEncoderVpx::CreateForVP8() {
	return scoped_ptr<VideoEncoderVpx>(new VideoEncoderVpx(false));
	}

	// static
	scoped_ptr<VideoEncoderVpx> VideoEncoderVpx::CreateForVP9() {
	return scoped_ptr<VideoEncoderVpx>(new VideoEncoderVpx(true));
	}

	VideoEncoderVpx::~VideoEncoderVpx() {}

	void VideoEncoderVpx::SetLosslessEncode(bool want_lossless) {
	if (use_vp9_ && (want_lossless != lossless_encode_)) {
	lossless_encode_ = want_lossless;
	codec_.reset(); // Force encoder re-initialization.
	}
	}

	void VideoEncoderVpx::SetLosslessColor(bool want_lossless) {
	if (use_vp9_ && (want_lossless != lossless_color_)) {
	lossless_color_ = want_lossless;
	codec_.reset(); // Force encoder re-initialization.
	}
	}

	scoped_ptr<VideoPacket> VideoEncoderVpx::Encode(
	const webrtc::DesktopFrame& frame) {
	DCHECK_LE(32, frame.size().width());
	DCHECK_LE(32, frame.size().height());

	base::TimeTicks encode_start_time = base::TimeTicks::Now();

	if (!codec_ \|\|
	!frame.size().equals(webrtc::DesktopSize(image_->w, image_->h))) {
	bool ret = Initialize(frame.size());
	// TODO(hclam): Handle error better.
	CHECK(ret) << "Initialization of encoder failed";

	// Set now as the base for timestamp calculation.
	timestamp_base_ = encode_start_time;
	}

	// Convert the updated capture data ready for encode.
	webrtc::DesktopRegion updated_region;
	PrepareImage(frame, &updated_region);

	// Update active map based on updated region.
	PrepareActiveMap(updated_region);

	// Apply active map to the encoder.
	vpx_active_map_t act_map;
	act_map.rows = active_map_height_;
	act_map.cols = active_map_width_;
	act_map.active_map = active_map_.get();
	if (vpx_codec_control(codec_.get(), VP8E_SET_ACTIVEMAP, &act_map)) {
	LOG(ERROR) << "Unable to apply active map";
	}

	// Do the actual encoding.
	int timestamp = (encode_start_time - timestamp_base_).InMilliseconds();
	vpx_codec_err_t ret = vpx_codec_encode(
	codec_.get(), image_.get(), timestamp, 1, 0, VPX_DL_REALTIME);
	DCHECK_EQ(ret, VPX_CODEC_OK)
	<< "Encoding error: " << vpx_codec_err_to_string(ret) << "\n"
	<< "Details: " << vpx_codec_error(codec_.get()) << "\n"
	<< vpx_codec_error_detail(codec_.get());

	// Read the encoded data.
	vpx_codec_iter_t iter = NULL;
	bool got_data = false;

	// TODO(hclam): Make sure we get exactly one frame from the packet.
	// TODO(hclam): We should provide the output buffer to avoid one copy.
	scoped_ptr<VideoPacket> packet(new VideoPacket());

	while (!got_data) {
	const vpx_codec_cx_pkt_t* vpx_packet =
	vpx_codec_get_cx_data(codec_.get(), &iter);
	if (!vpx_packet)
	continue;

	switch (vpx_packet->kind) {
	case VPX_CODEC_CX_FRAME_PKT:
	got_data = true;
	packet->set_data(vpx_packet->data.frame.buf, vpx_packet->data.frame.sz);
	break;
	default:
	break;
	}
	}

	// Construct the VideoPacket message.
	packet->mutable_format()->set_encoding(VideoPacketFormat::ENCODING_VP8);
	packet->mutable_format()->set_screen_width(frame.size().width());
	packet->mutable_format()->set_screen_height(frame.size().height());
	packet->set_capture_time_ms(frame.capture_time_ms());
	packet->set_encode_time_ms(
	(base::TimeTicks::Now() - encode_start_time).InMillisecondsRoundedUp());
	if (!frame.dpi().is_zero()) {
	packet->mutable_format()->set_x_dpi(frame.dpi().x());
	packet->mutable_format()->set_y_dpi(frame.dpi().y());
	}
	for (webrtc::DesktopRegion::Iterator r(updated_region); !r.IsAtEnd();
	r.Advance()) {
	Rect* rect = packet->add_dirty_rects();
	rect->set_x(r.rect().left());
	rect->set_y(r.rect().top());
	rect->set_width(r.rect().width());
	rect->set_height(r.rect().height());
	}

	return packet.Pass();
	}

	VideoEncoderVpx::VideoEncoderVpx(bool use_vp9)
	: use_vp9_(use_vp9),
	lossless_encode_(false),
	lossless_color_(false),
	active_map_width_(0),
	active_map_height_(0) {
	if (use_vp9_) {
	// Use I444 colour space, by default, if specified on the command-line.
	if (CommandLine::ForCurrentProcess()->HasSwitch(kEnableI444SwitchName)) {
	SetLosslessColor(true);
	}
	}
	}

	bool VideoEncoderVpx::Initialize(const webrtc::DesktopSize& size) {
	DCHECK(use_vp9_ \|\| !lossless_color_);
	DCHECK(use_vp9_ \|\| !lossless_encode_);

	codec_.reset();

	// (Re)Create the VPX image structure and pixel buffer.
	CreateImage(lossless_color_, size, &image_, &image_buffer_);

	// Initialize active map.
	active_map_width_ = (image_->w + kMacroBlockSize - 1) / kMacroBlockSize;
	active_map_height_ = (image_->h + kMacroBlockSize - 1) / kMacroBlockSize;
	active_map_.reset(new uint8[active_map_width_ * active_map_height_]);

	// (Re)Initialize the codec.
	if (use_vp9_) {
	codec_ = CreateVP9Codec(size, lossless_color_, lossless_encode_);
	} else {
	codec_ = CreateVP8Codec(size);
	}

	return codec_;
	}

	void VideoEncoderVpx::PrepareImage(const webrtc::DesktopFrame& frame,
	webrtc::DesktopRegion* updated_region) {
	if (frame.updated_region().is_empty()) {
	updated_region->Clear();
	return;
	}

	// Align the region to macroblocks, to avoid encoding artefacts.
	// This also ensures that all rectangles have even-aligned top-left, which
	// is required for ConvertRGBToYUVWithRect() to work.
	std::vector<webrtc::DesktopRect> aligned_rects;
	for (webrtc::DesktopRegion::Iterator r(frame.updated_region());
	!r.IsAtEnd(); r.Advance()) {
	const webrtc::DesktopRect& rect = r.rect();
	aligned_rects.push_back(AlignRect(webrtc::DesktopRect::MakeLTRB(
	rect.left(), rect.top(), rect.right(), rect.bottom())));
	}
	DCHECK(!aligned_rects.empty());
	updated_region->Clear();
	updated_region->AddRects(&aligned_rects[0], aligned_rects.size());

	// Clip back to the screen dimensions, in case they're not macroblock aligned.
	// The conversion routines don't require even width & height, so this is safe
	// even if the source dimensions are not even.
	updated_region->IntersectWith(
	webrtc::DesktopRect::MakeWH(image_->w, image_->h));

	// Convert the updated region to YUV ready for encoding.
	const uint8* rgb_data = frame.data();
	const int rgb_stride = frame.stride();
	const int y_stride = image_->stride[0];
	DCHECK_EQ(image_->stride[1], image_->stride[2]);
	const int uv_stride = image_->stride[1];
	uint8* y_data = image_->planes[0];
	uint8* u_data = image_->planes[1];
	uint8* v_data = image_->planes[2];

	switch (image_->fmt) {
	case VPX_IMG_FMT_I444:
	for (webrtc::DesktopRegion::Iterator r(*updated_region); !r.IsAtEnd();
	r.Advance()) {
	const webrtc::DesktopRect& rect = r.rect();
	int rgb_offset = rgb_stride * rect.top() +
	rect.left() * kBytesPerRgbPixel;
	int yuv_offset = uv_stride * rect.top() + rect.left();
	libyuv::ARGBToI444(rgb_data + rgb_offset, rgb_stride,
	y_data + yuv_offset, y_stride,
	u_data + yuv_offset, uv_stride,
	v_data + yuv_offset, uv_stride,
	rect.width(), rect.height());
	}
	break;
	case VPX_IMG_FMT_YV12:
	for (webrtc::DesktopRegion::Iterator r(*updated_region); !r.IsAtEnd();
	r.Advance()) {
	const webrtc::DesktopRect& rect = r.rect();
	int rgb_offset = rgb_stride * rect.top() +
	rect.left() * kBytesPerRgbPixel;
	int y_offset = y_stride * rect.top() + rect.left();
	int uv_offset = uv_stride * rect.top() / 2 + rect.left() / 2;
	libyuv::ARGBToI420(rgb_data + rgb_offset, rgb_stride,
	y_data + y_offset, y_stride,
	u_data + uv_offset, uv_stride,
	v_data + uv_offset, uv_stride,
	rect.width(), rect.height());
	}
	break;
	default:
	NOTREACHED();
	break;
	}
	}

	void VideoEncoderVpx::PrepareActiveMap(
	const webrtc::DesktopRegion& updated_region) {
	// Clear active map first.
	memset(active_map_.get(), 0, active_map_width_ * active_map_height_);

	// Mark updated areas active.
	for (webrtc::DesktopRegion::Iterator r(updated_region); !r.IsAtEnd();
	r.Advance()) {
	const webrtc::DesktopRect& rect = r.rect();
	int left = rect.left() / kMacroBlockSize;
	int right = (rect.right() - 1) / kMacroBlockSize;
	int top = rect.top() / kMacroBlockSize;
	int bottom = (rect.bottom() - 1) / kMacroBlockSize;
	DCHECK_LT(right, active_map_width_);
	DCHECK_LT(bottom, active_map_height_);

	uint8* map = active_map_.get() + top * active_map_width_;
	for (int y = top; y <= bottom; ++y) {
	for (int x = left; x <= right; ++x)
	map[x] = 1;
	map += active_map_width_;
	}
	}
	}

	} // namespace remoting